The invention relates to a system and method for monitoring repeatedly the absorption of electromagnetic radiation by a plurality of specimens occurring during a period of time. More particularly, this invention concerns a system and method in which each of a plurality of samples provides one or more aliquots which are subjected to chemical reaction with different reagents. The absorbance of each aliquot repeatedly is measured during a predetermined reaction time. The term "aliquot" as employed herein is a noun meaning a portion of a sample. The measurement involved herein is accurately ascertaining the absorbance of electromagnetic radiation at a particular wavelength by the fluids in the reaction vessels or cuvettes and converting the signals from an analog to a digital form so that the digital information can be processed, stored and manipulated in a computer.
It would be desirable to make such analysis in a continuous processing mode in which the apparatus can continue to operate so long as there are samples to be tested, the old samples and their tested aliquots being "replaced" by new samples and their aliquots without interruption of the operation of the testing apparatus. Such continuous operation may include one or more photometric measurements on a given aliquot by one or more photometers. It is preferable in receiving the analog absorbance signals each time a reaction vessel passes through a light beam that it be converted into a digital signal.
The continuous analyzers of interest typically supply sample aliquots to the reaction vessels which then are monitored by measuring the absorbance or transmittance by the fluids in the cuvettes of electromagnetic radiation at a particular wavelength or wavelengths. Sample fluids placed in the cuvettes or reaction vessels typically may be body fluids of a specific patient with one or more tests conducted on the sample fluids from each patient related to the patient's health; therefore, it is extremely critical that the signals obtained from the fluids in the cuvettes be both accurate and repeatable. The sample window, the base line and the position of the sample window with respect to the analog signal should be precisely repeatable for each cuvette and each light beam passing through the cuvette.
So far as known, prior art has not taught how to accomplish great accuracy and repeatability in practical devices. For example, optimization of the signals derived from the photometer beams passing through the cuvettes is not disclosed; wow in the rotating photometer carrier is not compensated for, etc.
The invention herein overcomes these and many other disadvantages to provide reliable, accurate and repeatable information on a continuous basis, capable of being processed in a high speed computer.